水稻模拟模型在高温敏感性研究中的应用

以调试校正较高精度的ORYZA2000模型参数及高温敏感性模拟验证为目的, 为模型适应性和本地化提供依据, 利用江苏省9个试验点5个水稻(Oryza sativa)品种的田间观测数据及当地逐日气象数据, 采用ORYZA2000最新版本(V2.13)水稻生长模型, 首先挑选出5个试验点3个品种的观测数据进行模型参数适应性调试校正, 确定了水稻发育生长阶段的各项参数, 然后用该参数对独立样本的4个试验点2个水稻品种地上部分各器官生物量、叶面积指数动态变化过程及最终产量进行了动态模拟。通过t检验和质量评价指标对模拟结果进行了显著性检验。利用通过检验的模型及其参数在假设环境温度不同时间段的持续升高条件下, 开展了高温对水稻生物量及产量影响的模拟研究, 模拟结果的影响幅度与实际高温处理结果的影响幅度进行了比较。结果表明: 1)经过调试校正获得较高精度的水稻发育阶段各参数, 较准确地模拟了水稻生物量和叶面积指数的动态累积过程, 模拟值与观测值基本一致, 说明校正后参数的合理性和有效性; 2)调整参数后高温敏感性模拟结果表明, 孕穗期到开花期温度连续3天、5天、7天升高到35 ℃时, 总生物量、穗生物量和总产量与对照(CK)相比分别下降了12%-25%; 不同时间段连续升高到38 ℃时下降18%-31%; 不同时间段升高到41 ℃时, 各生物量与对照相比分别下降了20%-38%。模型模拟值与控制试验室的观测数据的下降幅度基本一致, 表明经过参数校正的ORYZA2000可以应用于水稻对气温升高响应的预测。     

水稻模型ORYZA2000在湖南双季稻区的验证与适应性评价

校准与验证水稻生长模型ORYZA2000,为模型本地化、区域化研究应用提供依据。本文采用湖南双季稻区作物田间观测数据,结合栽培管理措施、土壤以及同期逐日气象数据等资料对ORYZA2000进行参数校正,调试确定了早稻、晚稻有代表性品种的作物参数;利用独立的数据资料,对双季稻生育期、叶面积指数、生物量、产量等指标的模拟结果进行了详细地验证与适应性评价。结果表明：模型对双季稻品种的生育期模拟较好,开花期和成熟期的相对模拟误差为1—2d;早稻和晚稻叶面积指数的归一化均方根误差（NRMSE）均为24%,地上部总生物量、绿叶生物量、茎生物量和穗生物量的NRMSE值分别为18%、22%、22%、24%和19%、24%、28%、28%,产量的NRMSE值分别为11%和16%。校验的作物参数反映了湖南早稻和晚稻品种的生物学特性,参数值合理、有效。通过校准作物参数,ORYZA2000可较为准确地模拟双季稻生长发育及其生物量的动态累积过程,适应性较强,能够应用于双季稻生产。     

Effects of spacing interval of wide bed planting on canopy characteristics and yield in winter wheat

2010-2012连续两年在大田试验条件下以多穗型品种‘百农矮抗58’为供试材料, 研究了宽幅播种(播幅8 cm)种植方式下不同带间距7 cm (KF7)、12 cm (KF12)和17 cm (KF17)对冬小麦(Triticum aestivum)冠层特征及产量的影响。结果表明: 与常规条播比较, 宽幅播种群体叶面积指数、平均叶倾角、光截获量、相对湿度、成穗数、生物量和产量较高, 而冠层开度和温度较低; 2010-2011年和2011-2012年宽幅播种成穗数和产量显著高于常规条播, 成穗数分别增加4.8%-16.4%和8.9%-21.0%, 产量分别提高2.96%-15.94%和4.09%-14.23%。宽幅播种下随带间距增大, 叶面积指数、平均叶倾角、光截获量、湿度及成穗数降低, 而冠层开度和温度升高; 穗粒数、千粒重、产量、生物量和收获指数以KF12最高, KF7最低。综合分析, 宽幅播种下12 cm带间距处理的小麦冠层结构合理, 微环境适宜, 产量最高, 可作为该种植方式的适宜带间距。     

Branching and metabolic exponents in seven woody plants

West、Brown和Enquist提出的植物分形网络模型(简称WBE模型)认为: 植物的分支指数(1/a, 1/b)决定植物的代谢指数, 当分支指数1/a、1/b分别为理论值2.0、3.0时, 代谢速率与个体大小的3/4次幂成正比, 但是恒定的3/4代谢指数并不能全面地反映植物的代谢情况。基于分支指数的协同变化, Price、Enquist和Savage对WBE模型进行扩展, 提出植物分支参数协同变化模型(简称PES模型)。该文借助于PES模型分析了7种木本植物的分支指数和代谢指数。结果表明: 物种间叶面积与叶生物量呈异速生长关系, 基于叶面积得到的分支指数1/a和代谢指数θ在物种间无显著差异, 基于叶生物量得到的分支指数1/a、1/b和代谢指数θ在物种间均存在显著差异, 但基于叶面积和叶生物量分别拟合出的整体分支指数1/a、1/b和代谢指数θ与理论值均无显著差异, 且用叶面积作为代谢速率的替代指标比用叶生物量分析得出的代谢指数与理论值更接近。今后研究应当关注植物叶面积与叶生物量的异速生长关系对植物代谢速率及相关功能特性的影响。     

水分异质性影响两种根茎型克隆植物赖草和假苇拂子茅的水分存储能力

水分在自然系统中呈异质性分布。有关水分异质性对克隆植物生长、形态和生理影响的研究已有大量的工作, 但是水分异质性对克隆植物存储能力, 尤其是水分存储能力影响的研究却十分缺乏。该文将两种根茎型克隆植物赖草(Leymus secalinus)和假苇拂子茅(Calamagrostis pseudophragmites)进行水分异质性和同质性实验处理, 探讨水分异质性对克隆植物水分存储能力、生长和形态的影响。在异质性水分处理下, 两种克隆植物的间隔子、枝和根的含水量均显著增加。两种克隆植物对水分异质性分布的适应策略有所不同, 赖草通过降低单个克隆分株的生长、提高芽的数量以应对水分异质性, 而假苇拂子茅通过增强整个分株种群的地下部分(根状茎、根和芽)生长来应对水分资源的异质性分布。水分储存能力的增强可以提高克隆植物适应水分异质性的能力。     

Research on characteristics of biomass distribution in urban forests of Shanghai metropolis based on remote sensing and spatial analysis

Aims
Monitoring and quantifying the biomass and its distribution in urban trees and forests are crucial to understanding the role of vegetation in an urban environment. In this paper, an estimation method for biomass of urban forests was developed for the Shanghai metropolis, China, based on spatial analysis and a wide variety of data from field inventory and remote sensing.
Methods
An optimal regression model between forest biomass and auxiliary variables was established by stepwise regression analysis. The residual value of regression model was computed for each of the sites sampled and interpolated by Inverse-distance weighting (IDW) to predict residual errors of other sites not subjected to sampling. Forest biomass in the study area was estimated by combining the regression model based on remote sensing image data and residual errors of spatial distribution map. According to the distribution of plantations and management practices, a total of 93 sample plots were established between June 2011 and June 2012 in the Shanghai metropolis. To determine a suitable model, several spectral vegetation indices relating to forest biomass and structure such as normalized difference vegetation index (NDVI), ratio vegetation index (RVI), difference vegetation index (DVI), soil-adjusted vegetation index (SAVI), and modified soil-adjusted vegetation index (MSAVI), and new images synthesized through band combinations such as the sum of TM2, TM3 and TM4 (denoted Band 234), and the sum of TM3, TM4 and TM5 (denoted Band 345) were used as alternative auxiliary parameters .
Important findings
The biomass density in urban forests of the Shanghai metropolis varied from 15 to 120 t·hm^-2. The higher densities of forest biomass concentrated mostly in the urban areas, e.g. in districts of Jing’an and Huangpu, mostly ranging from 35 to 70 t·hm^-2. Suburban localities such as the districts of Jiading and Qingpu had lower biomass densities at around 15 to 50 t·hm^-2. The biomass density of Cinnamomum camphora trees across the Shanghai metropolis varied between 20 and 110 t·hm^-2. The spatial biomass distribution of urban forests displayed a tendency of higher densities in northeastern areas and lower densities in southwestern areas. The total biomass was 3.57 million tons (Tg) for urban forests and 1.33 Tg for C. camphora trees. The overall forest biomass was also found to be distributed mostly in the suburban areas with a fraction of 93.9%, whereas the urban areas shared a fraction of only 6.1%. In terms of the areas, the suburban and urban forests accounted for 95.44% and 4.56%, respectively, of the total areas in the Shanghai metropolis. Among all the administrative districts, the Chongming county and the new district of Pudong had the highest and the second highest biomass, accounting for 20.1% and 19.18% of the total forest biomass, respectively. In contrast, the Jing’an district accounted for only 0.11% of the total forest biomass. The root-mean-square error (RMSE), mean absolute error (MAE) and mean relative error (MRE) of the model for estimating urban forest biomass in this study were 8.39, 6.86 and 24.22%, respectively, decreasing by 57.69%, 55.43% and 64.00% compared to the original simple regression model and by 62.21%, 58.50%, 65.40% compared to the spatial analysis method. Our results indicated that a more efficient way to estimate urban forest biomass in the Shanghai metropolis might be achieved by combining spatial analysis with regression analysis. In fact, the estimated results based on the proposed model are also more comparable to the up-scaled forest inventory data at a city scale than the results obtained using regression analysis or spatial analysis alone.     

磷肥对花生根系形态、生理特性及产量的影响

采用池栽, 测定不同施磷量对花生(Arachis hypogaea)根系性状、生理特性及产量的影响。结果表明: (1)结荚中期, 根系总长度、体积、表面积及根尖数量均随施磷量的增加而增加, 在施磷30-90 kg·hm^-2范围内, 施磷比不施磷4项指标分别增加3.5%-20.7%、9.3%-21.9%、9.7%-20.3%和12.6%-21.4%。特别是当施磷量超过60 kg·hm^-2时, 上述4项指标均显著高于不施磷处理; 施磷可使根系中超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT) 3种酶活性分别提高12.7%-20.6%、14.8%-36.8%和17.0%-41.8%, 丙二醛(MDA)含量降低8.4%-19.5%, 根系活力和可溶性蛋白含量分别提高10.4%-25.0%、29.2%-53.5%; 同时, 施磷可使单株根瘤数量和鲜重分别增加10.7%-21.7%和22.6%-35.6%。(2)收获期, 除MDA含量随施磷量的增加而增加, SOD、POD和CAT活性, 根系活力和可溶性蛋白含量均随施磷量增加而呈降低趋势, 但多数指标施磷与不施磷及不同施磷量之间差异不显著。造成这一现象的原因与施磷后花生荚果库容增大, 对光合产物需求量增加, 导致植株和根系营养不良, 加速衰老有关。(3)花生单株结果数、生物产量、经济系数、出米率及产量均随施磷量的增加而增加, 其中产量的增加主要是通过生物产量和经济系数协同提高来实现的。     

浙江天童常绿植物当年生与往年生叶片性状的变异与关联

植物叶片性状随叶龄的变化是植物生活史策略的体现, 反映了植物叶片的物质投资和分配方式。该研究通过在个体和物种2个水平, 比较浙江天童1 hm ²样地内常绿阔叶树种的平均叶面积(MLA)、比叶面积(SLA)和叶片干物质含量(LDMC)在当年生和往年生叶片间的差异和关联, 探究叶片物质分配策略在异龄叶间的变化, 并分析叶龄对植物叶片性状, 特别是叶片面积建成消耗的影响。结果显示: 1)在个体和物种水平上, MLA变异系数最大(个体: 79.5%; 物种: 66.5%), SLA次之(个体: 28.1%; 物种: 24.7%), LDMC较低(个体: 17.0%, 物种: 14.1%); 当年生叶片MLA、LDMC和SLA的变异系数均高于往年生叶片; 2)往年生叶MLA显著大于当年生叶(t = -38.53, p < 0.001), 往年生叶SLA显著小于当年生叶(t = 45.30, p < 0.001), 往年生叶LDMC显著大于当年生叶(t = -9.71, p < 0.001); 3)在个体水平, 当年生叶片MLA、SLA和LDMC值分别解释了往年生叶片MLA、SLA和LDMC变异的86%、48%和41%; 在物种水平, 当年生叶片MLA、SLA和LDMC值分别解释了往年生叶片MLA、SLA和LDMC变异的97%、83%和85%; 4) SLA在异龄叶间的变化表明, 与往年生叶片相比, 投资相同干物质, 当年生叶片可形成较大的叶面积, 其叶片面积建成消耗较小。研究认为, 植物叶性状在异龄叶间具有较大的变异性和关联性, 叶面积形成过程中生物量建成与消耗的协调可能影响植物叶片的发育。     

高寒草地狼毒枝-叶性状的坡度差异性

枝条与叶片的生长关系是植物形成不同冠层结构充分利用空间资源的一种策略, 有利于植株通过构型调整增强自身的光合效率和竞争力, 以适应不同的生境条件。在石羊河上游高寒退化草地, 利用ArcGIS建立研究区域的数字高程模型(DEM), 并提取样地坡度数据, 采用标准化主轴估计(SMA)方法, 研究了不同坡度狼毒(Stellera chamaejasme)种群枝与叶的生长。结果表明: 随着坡度增大, 狼毒叶大小、枝长度和分枝数均呈逐渐减小趋势; 狼毒分枝数与枝长度、叶片数与枝长度均呈异速生长关系, 枝长度增加的速度大于叶片数增加的速度, 分枝数增加的速度大于枝长度增加的速度; 不同坡度间的比较显示, 较大坡度上狼毒分枝数与枝长度、叶片数与枝长度的异速斜率均较大, 在枝长度一定的条件下, 较大坡度的狼毒具有更大的叶片数与枝长度的比值和分枝数与枝长度的比值。坡度差异造成环境因子和植被群落环境的变化, 进而影响狼毒的资源利用策略, 表现为枝条与叶片构型以及二者之间关系的变化, 反映了毒杂草较强表型可塑性的适应机制。     

Trade-off between the biomass and number of flowers in Stellera chamaejasme along an elevation gradient in a degraded alpine grassland

权衡关系是植物生活史对策理论的基础, 花大小-数量的权衡关系对理解花的生物量分配具有重要的意义。该文利用实验生态学方法, 研究了祁连山北坡高寒退化草地4个不同海拔狼毒(Stellera chamaejasme)种群花大小与花数量间的关系。结果表明: 随着海拔升高, 草地群落的高度、密度和地上生物量均呈先升高后降低的倒U型分布, 狼毒花大小呈逐渐增大的趋势, 而花数量呈相反的变化趋势; 不同海拔样地狼毒花大小与花数量间的相关性存在差异, 海拔2700、2900和3000 m样地狼毒花大小和花数量之间均存在极显著的负相关关系(p < 0.01), 海拔2800 m样地二者之间存在显著的负相关关系(p < 0.05), 狼毒植株分配给花大小与花数量的资源间存在着“此消彼长”的权衡关系; 海拔2800 m样地是狼毒植株花大小与花数量权衡关系由低海拔的花数量多而单花生物量低向高海拔的花数量少而单花生物量高转变的区域。狼毒植株通过合理权衡花数量和花大小的资源配置, 以补偿在海拔梯度上不利因素对种群繁衍带来的影响, 从而实现种群的繁殖成功, 反映了毒杂草对异质性生境的表型可塑性机制。     

Biomass estimation models and allocation patterns of 14 shrub species in Mountain Luya,Shanxi, China

Aims Shrub species have evolved specific strategies to regulate biomass allocation among various organs or between above- and belowground biomass and shrub biomass model is an important approach to estimate biomass allocation among different shrub species. This study was designed to establish the optimal estimation models for each organ (leaf, stem, and root), aboveground and total biomass of 14 common shrub species in Mountain Luya, Shanxi Province, China. Furthermore, we explored biomass allocation characteristics of these shrub species by using the index of leaf biomass fraction (leaf to total biomass), stem biomass fraction (stem to total biomass), root biomass fraction (root to total biomass), and root to shoot mass ratio (R/S) (belowground to aboveground biomass).
Methods We used plant height, basal diameter, canopy diameter and their combination as variables to establish the optimal biomass estimation models for each shrub species. In addition, we used the ratios of leaf, stem, root to total biomass, and belowground to aboveground biomass to explore the difference of biomass allocation patterns of 14 shrub species.
Important findings Most of biomass estimation models could be well expressed by the exponential and linear functions. Biomass for shorter shrub species with more stems could be better estimated by canopy area; biomass for taller shrub species with less stems could be better estimated by the sum of the square of total base diameter multiply stem height; and biomass for the rest shrub species could be better estimated by canopy volume. The averaged value for these shrub species was 0.61, 0.17, 0.48, and 0.35 for R/S, leaf biomass fraction, stem biomass fraction, and root biomass fraction, respectively. Except for leaf biomass fraction, R/S, stem biomass fraction, and root biomass fraction for shrubs with thorn was significantly greater than that for shrubs without thorn.     

玉米花生间作和磷肥对间作花生光合特性及产量的影响

揭示玉米(Zea mays)和花生(Arachis hypogaea)间作提高花生对弱光利用能力的光合特点及磷(P)肥效应, 对阐明间作花生适应弱光的光合机理和提高间作花生的产量具有重要意义。该试验于2011-2012年在河南科技大学试验农场分析了间作花生功能叶的叶绿素含量与构成、光响应曲线和CO₂响应曲线特点和荧光参数。结果表明: 与单作花生相比, 施P与不施P条件下玉米和花生间作显著(p < 0.01)提高了花生功能叶的叶绿素b含量, 降低了叶绿素a/b, 显著提高了光系统II最大光化学效率(F_v/F_m)、实际光化学效率(Φ_PSII)、光化学猝灭系数(q_P)、表观量子效率(AQY)和弱光时的光合速率, 显著降低了气孔导度、二磷酸核酮糖羧化酶羧化速率(V_cmax)、电子传递速率(J_max)和磷酸丙糖利用速率(TPU); 与不施P相比, 施P有利于提高间作花生功能叶的叶绿素含量, 显著提高了Φ_PSII、q_P、V_cmax、J_max和TPU, 说明间作花生通过提高功能叶的叶绿素b含量, 改变叶绿素构成, 提高了光系统II的F_v/F_m、Φ_PSII和q_P, 增强了对光能的捕获和转化能力, 提高了对弱光的利用能力, 而并非提高了对CO₂的羧化固定能力; 施P有利于提高间作花生对弱光的利用能力和产量, 土地当量比提高了6.2%-9.3%。     

山西不同生态型大豆品种苗期耐低温性综合评价

为探明山西不同生态型大豆(Glycine max)品种对苗期低温胁迫的应答表现, 寻求大豆苗期耐低温性综合评价指标和评价方法, 选取了山西普遍种植的‘晋大53’、‘晋大70’和‘晋豆24’ 3个不同生态型大豆品种, 在苗期将材料分别置于14、17和20 ℃人工气候箱中, 保持昼夜恒温, 进行低温胁迫处理。分别测定了各品种光合与产量性状值, 用基因型主效应及其与环境互作(GGE)双标图分析各性状对品种的效应及性状间的相关性, 应用隶属函数法综合评价各品种的苗期耐低温性。结果显示: 低温胁迫下不同生态型大豆品种苗期延长1-12天; 苗期光合性状值均下降, 其中, 叶片气孔导度(G_s)和蒸腾速率(T_r)下降最明显; 产量性状值均呈下降趋势, 单株生物量和单株荚数下降最明显; 各项性状在不同品种中对低温的应答效应不同, 且性状间存在明显的相关性, 可作为耐低温性的评价指标。品种‘晋大70’的耐低温性最佳。     

Responses of soil heterotrophic respiration to changes in soil temperature and moisture in a Stipa krylovii grassland in Nei Mongol

土壤异养呼吸在野外自然条件下除受温湿度影响外, 还受其他多种因子的综合影响, 很难利用野外观测数据确定土壤异养呼吸对温湿度变化的响应方程形式, 以及温湿度间是否存在交互作用。该研究在严格控制温湿度的条件下对内蒙古克氏针茅(Stipa krylovii)(西北针茅(Stipa sareptana var. krylovii))草原土样进行室内培养实验, 旨在解决上述问题。该研究的正交实验包括5个温度梯度(9、14、22、30、40 ℃)和5个湿度梯度(土壤持水力(water holding capacity, WHC)分别为20%、40%、60%、80%、100%)。室内培养实验持续71天, 土壤异养呼吸速率测定为2天(后期为1周)一次, 土壤可溶性有机碳和微生物生物量碳含量测定约为18天一次。研究结果显示: 土壤异养呼吸与温度呈显著正相关(p < 0.001)且温度间差异显著(p = 0.001), 呼吸温度敏感性(Q₁₀)与土壤水分含量呈正相关(p < 0.001); 呼吸与土壤水分二项式拟合效果较好, 在80% WHC时呼吸速率最大, 且最适湿度随温度上升而增加。土壤温度和水分的交互作用显著(p < 0.05), 土壤异养呼吸最适响应方程为lnRh = 0.914 + 0.098T + 0.046M + 0.001TM - 0.002T² - 0.001M² (Rh为异养呼吸, T为温度, M为湿度), 这说明加和形式的温湿度响应模型可能优于乘积形式。微生物生物量碳与土壤异养呼吸的相关性随培养时间发生变化, 土壤可溶性有机碳与土壤异养呼吸无显著相关(培养第20天除外), 原因可能是培养期间微生物死亡或群落结构改变导致微生物总体代谢活性的变化。     

Nitrogen and yield potential of irrigated rice

Yield potential of modern rice varieties and implications for N management were evaluated in a series of field studies that provided data for validation of an eco-physiological simulation model for rice. We tested the hypothesis that N was the major factor limiting yield potential of irrigated rice. The simulation model ORYZA1 was used to evaluate the observed yield differences between varieties grown with different N management and in different environments. The model explained differences in yield of the treatments resonably well on the basis of differences in radiation, temperature, leaf N content and variety coefficients for phenological development. It was demonstrated by the model and experimental data that yield levels of 6 t ha^-1 in the wet season and 10 t ha^-1 in the dry season can be obtained in the tropics with the current short duration varieties only when the N supply from soil and fertilizer is adequately maintained at key growth stages. Yield probabilities for rice crops were simulated for different environments using long term weather data at two Philippine sites.     

Effects of a winter wildfire on plant community structure and forage quality in subalpine grassland of western Sichuan,China

火是继土壤、水分、温度之后, 塑造地表植被的主要力量。该文以2010年“12·5”冬草场火烧事件为背景, 通过对比川西亚高山草地火烧区域和未火烧区域火后第一年植被群落结构和牧草质量, 探讨亚高山草地植被对冬季火烧的响应机制。通过物种多样性分析、双向指示种分析(TWINSPAN)和干重等级法(dry-weight-rank)分析发现, 冬季火烧未改变植被的生物多样性、均匀度和物种丰富度, 却改变了植被群落结构的物种组成。冬季火烧导致一年生禾草、一年生杂草、灌木等3种生活型植物的数量和生物量增加; 多年生杂草数量减少, 生物量增加; 多年生禾草数量和生物量减少。冬季火烧也极大地减少了可食禾草的比例, 增加了各种杂草的生物量比例。此次火烧事件降低了细柄草(Capillipedium parviflorum)和早熟禾(Poa sp.)等可食禾草的竞争能力, 增加了一些杂草(如火绒草(Leontopodium leontopodioides)、白莲蒿(Artemisia sacrorum)、草玉梅(Anemone rivularis)等)在资源竞争中的相对优势, 最终表现为火后牧草的可食性下降。     

Biomass allocation patterns of Loropetalum chinense

Aims Biomass is the most fundamental quantitative character of an ecosystem. Biomass allocation patterns reflect the strategies of plants to adapt various habitat conditions and play a vital role in evolution, biodiversity conservation and global carbon cycle. Loropetalum chinense shrub is one of the most dominant shrub types in subtropical China. The objectives of this study were to quantify the allometric relationships and the biomass allocation pattern among organs, and to investigate the effects of body size, shrub regeneration origin and site factors on allometry and biomass allocation.
Methods Individual samples of L. chinense were harvested from shrublands in subtropical China and were further divided into leaves, stems and roots. The allometric relationships between different organs were modeled with standard major axis (SMA) regression and the biomass allocation to different organs was quantified. The effects of body size, shrub regeneration origin and other habitat factors on allometry and allocation were examined using Pearson’s correlation analysis and multiple linear regressions.
Important findings The isometric scaling relationships between shoot and root changed to allometric relationships with increasing basal diameter. The scaling relationships between leaf and stem and between leaf and root were isometric for smaller diameter classes, while for larger diameter classes they were allometric. These relationships were significantly different among shrub regeneration origin types. The scaling relationships between different organs were not affected by habitat factors; while the coverage of shrub layer and slope affected biomass allocation due to their influences on the allometric relationships between different organs at the initial stage of growth. The mean dry mass ratios of leaf, stem, root and the mean root to shoot ratio were 0.11, 0.55, 0.34 and 0.65, respectively. With the increase of basal diameter class, stem mass ratio (0.50-0.64) increased, while leaf mass ratio (0.12-0.08) and root mass ratio (0.38-0.28) decreased, and consequently root to shoot ratio (0.91-0.43) also decreased. In secondary shrublands, the leaf mass ratio was 0.12 and the root mass ratio was 0.33, while these values were 0.07 and 0.36 respectively in natural shrublands. The ratio of aboveground allocation was significantly correlated to shrub layer coverage (r = 0.44, p < 0.05). Leaf mass ratio was significantly correlated to slope (r = -0.36, p < 0.05) and root mass ratio was significantly correlated to mean annual temperature (r = 0.34, p < 0.05). Results showed that with the increase of body size, the scaling relationships between different organs of L. chinense changed from isometric to allometric, and more biomass was allocated to aboveground part, and concretely, to stems. Human disturbance affected biomass allocation by its influences on the allometric relationships between different organs, and by increasing biomass allocation to leaves and decreasing allocation to roots. Reduced light resource promoted the biomass allocation to aboveground part, and higher slope resulted in decreased biomass allocation to leaves, while higher mean annual temperature promoted biomass allocation to roots. The variation in annual precipitation had no significant influences on biomass allocation. The biomass allocation strategies of L. chinense partially support the optimal partitioning theory.     

Carbon density and its spatial distribution in the Potentilla fruticosa dominated alpine shrub in Qinghai,China

Aims Shrub recovery is recognized as an important cause of the increase of carbon stocks in China, and yet there are great uncertainties in the carbon sink capacities of shrubs. Our objectives were to estimate carbon density and its spatial distribution in alpine shrubs.
Methods Eight sites in Potentilla fruticosa dominated shrublands across Qinghai, China were investigated. Plant biomass and carbon content in leaves, branches and stems, and roots were measured to analyze the biomass allocation and carbon density.
Important findings Mean carbon densities in biological carbon, litter, soil and whole ecosystem of P. fruticosa shrublands were 5088.54, 542.1, 35903.76 and 41534.4 kg·hm^-2, respectively. Carbon density in the shrub layer was more than 68% of the biological carbon density of the whole ecosystem and was mainly distributed in roots (49.5%-56.1%). Carbon density of the herbaceous layer was 22.5% of the biological carbon density of the whole ecosystem and was also mainly distributed in roots (59.6%-75.1%). The biological carbon density of P. fruticosa shrublands (5.08 t·hm^-2) was lower than the average carbon density of shrub communities in China (10. 88 t·hm^-2). Soil carbon density contributed the largest proportion (85.8%) of total carbon density in P. fruticosa shrublands.     

Biomass allocation and leaf stoichiometric characteristics in four desert herbaceous plants during different growth periods in the Gurbantünggüt Desert,China

荒漠草本植物是荒漠生态系统物种多样性的主体, 对其生物量分配及叶片化学计量特征随植物生长的变化规律的研究有助于深入了解荒漠草本植物生存策略和功能特征。该文选择古尔班通古特沙漠4种优势草本(2种短命植物, 2种一年生长营养期植物)为研究对象, 通过野外原位多时段取样, 对比研究了四者生物量分配、叶片N-P化学计量学随植物生长的变化特征, 以及二者之间的关系。结果表明, 在生物量累积过程中, 4种植物根冠比逐渐减小, 地上与地下生物量间的相关生长关系也发生变化, 其中琉苞菊(Hyalea pulchella)和角果藜(Ceratocarpus arenarius)的相关生长指数先增加后减小, 并趋于稳定, 而尖喙牻牛儿苗(Erodium oxyrrhynchum)和沙蓬(Agriophyllum squarrosum)的相关生长指数由小到大并趋于等速生长。琉苞菊叶片N、P含量呈逐渐增长趋势, 而另外3种植物呈下降趋势, 表明所研究的荒漠植物在生长过程中, 叶片N-P化学计量发生改变, 叶片化学计量特征与生物量指标的相关性较弱。     

Present status and rate of carbon sequestration of forest vegetation in Jilin Province,Northeast China

Aims
Forests represent the most important component of the terrestrial biological carbon pool and play an important role in the global carbon cycle. The regional scale estimation of carbon budgets of forest ecosystems, however, have high uncertainties because of the different data sources, estimation methods and so on. Our objective was to accurately estimate the carbon storage, density and sequestration rate in forest vegetation in Jilin Province of China, in order to understand the role of the carbon sink and to better manage forest ecosystems.
Methods
Vegetation survey data were used to determine forest distribution, size of area and vegetation types regionally. In our study, 561 plots were investigated to build volume-biomass models; 288 plots of shrubs and herbs were harvested to calculate the biomass of understory vegetation, and samples of trees, shrubs and herbs were collected to analyze carbon content. Carbon storage, density and sequestration rate were estimated by two forest inventory data (2009 and 2014), combined with volume-biomass models, the average biomass of understory vegetation and carbon content of vegetation. Finally, the distribution patterns of carbon pools were presented using ArcGIS soft ware.
Important findings
Understory vegetation biomass overall was less than 3% of the tree layer biomass, varying greatly among different forest types and even among the similar types. The carbon content of trees was between 45.80%-52.97%, and that of the coniferous forests was higher than that of the broadleaf forests. The carbon content of shrub and herb layers was about 39.79%-47.25% and 40%, respectively. Therefore, the vegetation carbon conversion coefficient was 0.47 or 0.48 in Jilin Province, and the conventional use of 0.50 or 0.45 would cause deviation of ±5.26%. The vegetation carbon pool of Jilin Province was at the upper range of regional carbon pool and had higher capacity of carbon sequestration. The value in 2009 and 2014 was 471.29 Tg C and 505.76 Tg C, respectively, and the total increase was 34.47 Tg C with average annual growth of 6.89 Tg C·a^-1. The corresponding carbon sequestration rate was 0.92 t·hm^-2·a^-1. The carbon density rose from 64.58 t·hm^-2 in 2009 to 66.68 t·hm^-2 in 2014, with an average increase of 2.10 t·hm^-2. In addition, the carbon storage of the Quercus mongolica forests and broadleaved mixed forests, accounted for 90.34% of that of all forests. The carbon increment followed the order of young > over-mature > near mature > middle-aged > mature forests. The carbon sequestration rate of followed the order of over-mature > young > near mature > middle-aged > mature forests. Both the carbon increment and the carbon sequestration rate of mature forests were negative. Furthermore, spatially the carbon storage and density were higher in the east than in the west of Jilin province, while the carbon increment was higher in northeast and middle east than in the west. The carbon sequestration rate was higher in Tonghua and Baishan in the south, followed by Jinlin in the middle and Yanbian in the east, while Baicheng and Songyuan, etc. in west showed negative values.